Effect of free-range access, shelter type and weather conditions on free-range use and welfare of slow-growing broiler chickens

Mean percentage of birds using the free-range area was higher in SRC than in AS groups (42.8% vs. 35.1%; F1,7 = 1180.00, P < 0.001). The mean percentage of animals located further than 5 m from the house was 10.6 ± 1.1% of the chickens that were outside in the SRC groups vs. 4.1 ± 0.8% in the AS groups (F1,7 = 24.03, P = 0.002). The interactions of shelter type with rainfall (F2,5578 = 70.59, P < 0.001), increasing radiation (F2,5578 = 300.93, P < 0.001) and increasing wind speed (F2,5578 = 14.77, P < 0.001) showed that these factors were related with fewer chickens being outside; and that these effects were more pronounced in SRC than in AS chickens. An increasing temperature was related with more free-range use (F1,5578 = 32.24, P < 0.001). A shorter TI duration in week 3 (at group level) was associated with more chickens further than 5 m from the house (F1,250 = 13.79, P < 0.001). The percentage of animals needing more than one induction to induce TI in week 10 was higher for chickens from SRC (29.7%) than from IN groups (4.8%; t102 = −2.61, P = 0.028) but not AS (14.8%). Hock dermatitis occurred less in AS (7.6%) than in IN (40.1%; t222 = 3.15, P = 0.005) but not SRC (13.7%). These findings indicate that presence of SRC was most effective in encouraging chickens to use the free-range area, but that free-range access was only moderately related to better leg health and fearfulness (at group level).